Chlorine and peracetic acid stability in real world environmental workflows
Tracks
Tāwhirimātea 2
| Thursday, August 27, 2026 |
| 2:20 PM - 2:40 PM |
| Tāwhirimātea 2 |
Overview
Liz Orr
Speaker
Mrs Liz Orr
Manager Infection Prevention And Surveillance Service
Royal Melbourne Hospital
Chlorine and Peracetic Acid Stability in Real World Environmental Workflows
Abstract
Chlorine based disinfectants such as sodium hypochlorite remain widely used in healthcare due to their broad antimicrobial activity, although their performance is influenced by concentration, pH, temperature, organic load and storage conditions. Peracetic acid-based disinfectants offer an alternative with broad spectrum efficacy. This study evaluated the stability of chlorine and peracetic acid solutions across routine environmental workflows to quantify concentration over time.
An evaluation was undertaken to assess the stability of chlorine solutions at 1000 and 5000 parts per million (ppm) and peracetic acid prepared according to manufacturer instructions. Solutions were tested under controlled conditions using laundered reusable mops and buckets. DPD photometry was compared with titration and test strips to identify the most reliable verification method. Time‑point sampling for bucket solutions and expressed mop liquid occurred at baseline and multiple intervals up to 24 hours. Chlorine dosing systems used to create standardised dilution strengths were also evaluated to measure dosing accuracy.
Chlorine concentration demonstrated substantial variability across all conditions with notable degradation in both unopened bottles and prepared solutions. Mop contact was the strongest driver of concentration loss, particularly with double‑dipping workflows. Expressed mop liquid concentrations consistently delivered significantly lower concentration than bucket values, indicating that disinfectant applied to surfaces was weaker than intended. The dilution system validation revealed large variability in the dosing system performance resulting in inaccurate starting concentrations. Peracetic acid displayed greater initial stability in closed containers, but similar decline when applied to mops, with reusable mop types requiring the greatest demand.
These findings highlight gaps between intended and actual chemical delivery during terminal isolation cleaning. Reliable disinfection requires validated dosing systems, avoidance of double dipping, and correct concentration of disinfectants. Peracetic acid may offer workflow advantages but requires protocols that minimise mop associated concentration loss.
An evaluation was undertaken to assess the stability of chlorine solutions at 1000 and 5000 parts per million (ppm) and peracetic acid prepared according to manufacturer instructions. Solutions were tested under controlled conditions using laundered reusable mops and buckets. DPD photometry was compared with titration and test strips to identify the most reliable verification method. Time‑point sampling for bucket solutions and expressed mop liquid occurred at baseline and multiple intervals up to 24 hours. Chlorine dosing systems used to create standardised dilution strengths were also evaluated to measure dosing accuracy.
Chlorine concentration demonstrated substantial variability across all conditions with notable degradation in both unopened bottles and prepared solutions. Mop contact was the strongest driver of concentration loss, particularly with double‑dipping workflows. Expressed mop liquid concentrations consistently delivered significantly lower concentration than bucket values, indicating that disinfectant applied to surfaces was weaker than intended. The dilution system validation revealed large variability in the dosing system performance resulting in inaccurate starting concentrations. Peracetic acid displayed greater initial stability in closed containers, but similar decline when applied to mops, with reusable mop types requiring the greatest demand.
These findings highlight gaps between intended and actual chemical delivery during terminal isolation cleaning. Reliable disinfection requires validated dosing systems, avoidance of double dipping, and correct concentration of disinfectants. Peracetic acid may offer workflow advantages but requires protocols that minimise mop associated concentration loss.
Biography
Liz Orr is an Infection Prevention Clinical Nurse Consultant and the Manager of Infection Prevention and Surveillance Service at The Royal Melbourne Hospital. She has led her team through the COVID-19 pandemic. Liz has held Infection Prevention Clinical Nurse Consultant positions with Hand Hygiene Australia, VICNISS, Austin Health and Monash Health. She has completed studies in Leadership and Master of Public Health. Liz is a member of the Australasian College of Infection Prevention and Control and sits on the VICNISS Advisory Committee. She has published research in antimicrobial stewardship and COVID with multiple presentations at conferences.
Associate Professor Marshall is an infectious diseases physician and is head of the Infection Prevention and Surveillance Service at The Royal Melbourne Hospital. She is also honorary principal research fellow at the Department of Infectious Diseases at The University of Melbourne. She has broad interests including hospital ventilation, waterborne pathogens and cleaning as well as surveillance of healthcare associated infections.
Anna Denton is a third‑year Bachelor of Science student at La Trobe University, majoring in Biochemistry with a Human Physiology and Neuroscience minor. She is a recipient of the Bachelor of Science Provost's Commendation and multiple Metabolic Biochemistry Excellence awards. During a recent placement elective, she collaborated on a research project evaluating the efficacy of various biocides in a clinical environment. Her academic interests include biochemistry, chemistry, and human biosciences, and she aspires to contribute meaningfully to science and healthcare.
